1. Field of the Invention
The present invention relates to a key button structure applied to a portable terminal device such as a mobile phone, PHS (Personal Handyphone System), PDA (Personal Data Assistance, Personal Digital Assistants: Personal Portable Information Communication Device), and more particularly to a key button structure for displaying a plurality of characters assigned to respective key buttons and a portable terminal device therewith.
2. Description of the Prior Art
A recent mobile phone includes a telephone book function and a mail function, where characters such as numerals, kana characters and alphabetical letters are often entered by operating key buttons.
Such a mobile phone has restrictions on size and weight, which limits spaces of a key operation section and number of key buttons. Accordingly, a plurality of types of characters such as numerals, kana characters and alphabetical letters are assigned to one key button.
FIG. 13 is a view illustrating an example of a conventional plurality of types of characters assigned to a ten-key and symbol keys of the key operation section.
A plurality of types of characters such as numerals, kana characters and alphabetical letters are respectively assigned to respective key button of a ten-key.
For a user to enter characters, a character indicated on a key button is visibly verified, and a key button corresponding to a desired character is looked for and depressed in accordance with an entry mode. However, it is necessary to visibly verify a desired character and select a key corresponding to the character from respective keys assigned with a plurality of types of characters, and indicated characters are difficult to visibly verify. Accordingly, entry speed lowers or an erroneous entry occurs.
To improve the visibility of a displayed character on a key button, Japanese Patent Laid-Open Publication No. 2001-6479 (Patent Document 1) discloses a switch button capable of improving the visibility by forming characters such as numerals and kana characters into a recessed shape on a rear face of a button main-body constituted of a transparent material and coloring the recessed portion so that the displayed characters may look three-dimensional by the lighting from the rear face.
Japanese Patent Laid-Open Publication No. 2002-320005 (Patent Document 2) discloses a key structure for portable terminal equipment capable of enlarging display areas and display sizes for high visibility by indicating a kana character and alphabetical letters on the front side of a transparent key body having a prescribed thickness and indicating a numeral on the rear side of the key body.
The switch button disclosed in Patent Document 1 makes it easy to see characters because the characters such as numerals and kana characters formed in a recessed pattern are displayed in three dimensions, however, concurrently displays the plurality of characters such as numerals and kana characters formed in a recessed pattern. In selecting a targeted character in accordance with an entry mode, characters other than the character to be entered are also displayed. This inhibits a targeted character from being looked for, thus speedy entry becomes difficult, and an erroneous entry is apt to occur.
The key structure for portable terminal equipment disclosed in Patent Document 2 makes it easy to see characters because a targeted character is enlarged and displayed on both faces of the front and side of a key body, however, the characters indicated respectively on both faces of the front and side of the key body are overlapped by each other so as to be invisible. In selecting a targeted character in accordance with an entry mode, characters other than the character to be entered are also displayed. This inhibits a targeted character from being looked for, thus speedy entry becomes difficult, and an erroneous entry is apt to occur.
For example, in making an entry in kana entry mode, a targeted kana character looks overlapped with alphabetical letters or a numeral other than a kana character assigned to a key button, therefore the kana character is not easy to look for. This lowers entry speed and frequently causes erroneous entries.